Apparatus for continuous treatment of moving strands



June 16, 1964 RYUJI YosHuKE APPARATUS FOR CONTINUOUS TREATMENT OF MOVING STRANDS Filed Sept. 22, 1960 3 Sheets-Sheet 1 53 INVENTOR. Hyw/ yosH//KE ATTORNEY June 16, 1964 RYU'JI YosHuKE APPARATUS FOR CONTINUOUS TREATMENT oF MovTNG sTRANDs Filed sept. 22, 1960 3 Sheets-Sheet 2 allllllflitllVFIIIIIIIIIIAE il Ilaf ,u

flillllit RYUJ/ YOSH//KE 1N V EN TOR.

TTOR/VEY June 16, 1964 RYUJI YosHnKE 3,137,151

APPARATUS FOR coNTINUoUs TREATMENT oF NovING sTRANDs Filed Sept; 22. 1960 3 Sheets-Sheet 3 IHIIIIW HIIIHI F/G. 4 l F/G- 5 FIG. 5A /08 INVENTOR. RYUJ/ YOSH//KE ATTORNEY Y 3,137,151 APPARATUS FOR CONTlNUOUS TREATMENT F MOVING STRANDS Ryuii Yoshiike, Saidaiji, Japan, assigner to American Cyanamid Company, New York, N.Y., a corporation of Maine Filed Sept. 22, 1960, Ser. No. 57,692 Claims priority, application Japan Dec. 22, 1959 6 Claims. (Cl. 68--5) This invention relates broadly to certain new and useful improvements in apparatus for the iluid treatment of strands of elongated materials'. More particularly it is concerned with a new and improved apparatus for treating natural and synthetic monolaments and multi-filaments with uid media in'liquid or vapor state during their travel from one point to another. Examples of such lamentary materials are those made from berformable, thermoplastic homopolymers and copolymers of both the condensationandr addition-polymerization types.

f The present invention relates particularly to certain new and useful improvements in apparatus which is especially adapted for use in continuously treating polyacrylonitrile lamentary material, specically a tow or a continuous lamentary yarn comprised of a fiber-formable polymer of acrylonitrile. Such a polyacrylonitrile lilamentary material may be comprised of as little as, for example, 35% by weight of a polymer of acrylonitrile. Advantageously the polyacrylonitrile lamentary material is comprised of a polymer of acrylonitrile containing a major proportion (preferably at least 70%) of, by weight, acrylonitrile combined in the polymer molecule. The acrylonitrile polymer may be a homopolymer or a copolymer of acrylonitrile, or it may be a blend in which the lamentary material is produced from a blend of two different polymers, the acrylonitrile content of which is at least 70% by weight of combined acrylonitrile. The apparatus of the invention is obviously not limited to its use only in continuously treating contniuously moving strands of polyacrylonitrile lamentary material, but it also can be used in continuously treating moving strands comprised of other natural and synthetic iilame'ntary materials, or strands comprised of other materials.

The terms strand, strands, structure and structures? asused generically herein (including the claims in the case of strand and strands) is intended to include Within its meaning elongated materials in any form, including monolaments and multifilaments inyarn, thread, fabric, rod, tape, ribbon, strand, rope, bundle, tow, sliver, or other form, and also elongated sheets, films and the like, and which are of continuous (i.e., indefinite) length. It was known prior to the present invention that polymeric acrylonitrile strands or structures which do not brillate, or which ibrillate only to a negligible degree, can be produced by subjecting a lamentary material or other structure comprised of a polymer of, acrylonitrile to a relatively high temperature and pressure in the presence of saturated or wet steam. The known prior art is disclosed in, for example, U.S. Patent No. 2,708,843, dated'May 24, 1955, and in the art referred to therein. Other prior art includes U.S. Patent No. 2,932,183, dated April Y12, 1960, which is concerned primarily with a pres- `surir/.edhsealing device for eliminating leakage from a pressurized chamber in the interior of which a heattreating or annealing operation is carried out on a continuously moving tow of synthetic material, speciiically a polyacrylonitrile filamentary mateiral.

As indicated hereinbefore, various kinds of lilamentary materials have been treated with afluid medium at an United States Patent i of producing ilamentary materials. Such problems are its temperature suiciently, it is generally necessary for the fluid treating medium to be under superatmospheric pressure, many problems from an apparatus viewpoint arise in cases where the heat-treatment is carried out in a continuous process, for example in a continuous process less numerous when the heat-treatment is carried out batch-wise, for instance in an autoclave. However, in the n design and construction of apparatus for the continuous modification is the same as the outlet section;

elevated temperature under `superatmospheric pressure to improve their useful properties. Since, in order to raise treatment of a continuously moving strand, there is the problem or requirement of preventing leakage of the pressurized medium from the treating vessel to the outside atmosphere while the strand is passing through the inlet and outlet ports of the vessel. Another problem is that of providing means for automatically adjusting the diameterof the inlet and outlet passageways through which the strand passes, and especially when the size of the strand is suddenly changed by, for example, a knot. Still another problem is that of eiecting the treatment Without disturbing the form of the strand, which usually is arranged in the form of a flat band or ribbon so as to be heat-treated uniformly. Another problem is that of avoiding any entanglement or twist of the lamentary material during its passage through the inlet and outlet ports of the treating or pressure vessel. Still another problem is that ofV avoiding damage to the quality of the lilamentary material as a result of maintaining the strand at an elevated temperature under superatmospheric pressure for too long a period of time.

The present inventor, as Vthe result of extensive investigational and design work, has devised apparatus for continuously treating continuously moving strands of elongated material, more particularly filamentary material, by which the aforementioned problems-are satisfactorily solved and the requirements fulfilled. The apparatus is understood most readily from the following detailed description thereof when considered in connection with the accompanying drawing, which is illustrative of the invention, and in which FIG. `1 is a vertical, sectional view which is illustrative of one embodiment of the invention; FIG. 2 is a vertical, sectional view which is illustrative of another embodiment of the invention;

2 FIG. 3 is a vertical, sectional, broken view of apparatus similar to that shown in FIG. 2 but differing therefrom in'that a mechanism for stretching is provided in the main body portion of the pressure vessel;

FIG. 4 is a vertical, sectional view of part of the apparatus shown in FIGS. 1 and 2, more particularly an inlet section of the pressure vessel, and with a minor FIG. 5 is a front view, from the right side, of the inlet section shown in FIG. 4; FIG. 5A is a side View, from the right side, `of the inlet section shown in FIG. 5; and .1 FIG. 6 is a vertical, sectional view of a modied form of inlet and outlet sections that can be used in the embodiments of the invention illustrated in FIGS. l and 2.

In the various figures the same reference numerals represent the same parts. i With particular reference to the drawing the treating or pressure vessel 10 shown in FIGS. 1, 2 and 3 may be either U-shaped or J-shaped, the embodiment shown in FIG. l being J-shaped. In FIG. 1 a bundle of filamentary material 12 (i.e., a strand)u from a previous step in the process `is first passed between rolls 14whereby the form of the bundle is converted to a flat, belt-like shape.

Patented June 16, 1964r The bundle is then passed through the inlet port 16 wherein the ilamentary material, after passing through the inlet port 16, passes between the nip rolls 18. These rolls are positioned within the treating or pressure vessel 10, which is kept at an elevated temperature' and underV a superatmospheric pressure. Since the filamentary material is thus introduced into an area of superatmospheric pressure from the ordinary pressure area at this step, it tends always to be pulled back toward the outside by the action of the pressurized medium. It is therefore necessary that the nip rolls 18 nip the lamentarymaterial with suicient strength or force required to resist anyaction that would cause disarrangement of thelamentary material. However, if one holds the ilamentary material under heat with an excessive pressure, there results degradation of the quality of the lamentary material due to such influencing factors as, for instance, adhesion, etc. It is therefore necessary to cool the nip rolls 18 as much asis possible.

Cooling of the nip rolls may be done, for example, by passing cooling water through them. To do this, water from a supply source (not shown) is pumped under pressure by the pump 20 through the conduit 22 to the inlet y end of the central axis 24 of each of the nip' rolls V318. The cooling water leaves the opposite, outlet end of the central axis of eachof the nip rolls through the conduit 26. It was found that when operating the apparatus in this manner there was a tendency for the ilamentary material to wrap up on the nip rolls. Such wrap-ups occurred, it is believed, because the lamentary material was somewhat warm when introduced to the nip of the nip rolls and because of the adverse effect upon the ilaments due to the tension required to pull the strand against the above-described action of the pressurized -medium. To obviate wrap-ups itis preferred that water be blown through nozzles 28 located beneath the nip rolls 18 in such a position that the water is directed toward the point of contact of the nip with the strand. The water leaving the outlet end ofthe central axis of each of the nip rolls through the conduit 26 advantageously may be employed as the water that is fed to the nozzles 28 for spraying upon the strand as it leaves the nip of the rolls.

The strand 12 next passes to basket rolls 30, which loosely hold the strand. From these basket rolls the Strand passes to the oscillating funnel 32 attached to the lever 34. The funnel is oscillated from right to left (and from left to right) by conventional oscillating mechanism (not shown)` and which is located outside of the pressure vessel 10. The oscillating funnel shakes down the strand and piles it up in a plurality of folds in the treating vessel 10 (FIG. l) and wherein it Vis heat-treated in a relaxed state for the required period of time. The residence time in the treating vessel is controlled by adjusting the drawof rate of the strand with the feed-in rate so as to provide the desired residence time.

IThe temperature of the hot fluid medium, e.g., hot water, steam, hot aqueous salt solution, etc., is determined by any suitable means, e.g`., by a thermocouple (or a plurality of thermocouples), two of which, i.e., thermocouple 36, are shown in the wall of the vessel l0. Conduit 38 provides means for supplying heating medium from a supply source (not shown) to the treating vessel. The amount of heating medium which is introduced to the treating vessel can be automatically controlled bythe automatic adjustment of the diaphragm valves 40. In this way the temperature of the-hot uid medium in the treating vessel can be kept at the desired point.

. .At the end of the required heat-treating period the heattreated strand is pulled from the treating'vessel 10 by means of draw-off rolls 42 after passing over or through (as the case may be) guide bar 44, guide ring 46 and guide bars 48, and through the outlet port 50 which is equipped with the s'ame'mechanisrn as the inlet port l16. Any excessY fluid medium or condensate resulting from the condensation of steam (when steam is the fluid medi-` um) can be removed from` the vessel l@ (FGS. 1, 2 and 3), if and when desired, through the conduit 51 provided with the valves 53.

A more detailed description of the construction and operation of the improved pressure-sealing means cornprising the inlet and outlet ports will be given later herein. Y

From the draw-off rolls 42 the strand is conducted to the next step in the process.

With more particular reference to FIG. 2, the pressure vessel 10 [there illustrated is shaped much like a U. This vessel is comprised of a main body portion 52provided at one end with an inlet section or feed-in tower S4 and an outlet section or draw-off tower 56 at the other end. The main body portion 52 is preferably in a horizontal position, and the feed-in and draw-.oi towers arevpreferably perpendicular or substantially perpendicular to the aforesaid main body portion. Inlet port 16 is located at the top of feed-in tower 54 while outlet'port 5t) is located at the top of draw-off tower 56. c

The mechanism in the feed-in .tower 54 is essentially the same as that which is present in the inlet section of thepressure vessel shown in FIG. l. Thus, it contains the nip krolls 18, the basket ,rolls 34B and the oscillating funnel 32. The oscillating motion of this funnel is effected by torsion of the lever 34 connected with the funnel 32.

An endless conveyor 5S is positioned in the main body portion 52 of the treating vsel 10 so that the strand leaving the oscillatingfunnel 32 is laid down on .the conveyor at its feed-on end beneath the feed-in tower 54 and iscarried on the conveyor tothe opposite end of the main body portion off the treating vessel. The moving conveyor withthe strandthereon is caused to move by driving mechanism (not shown) at a rate such that the strand will receive a i heat ,treatment for the desired period of time.

In the draw-off tower 56 guide bars. 48 and 60 are provided for leading the ystrand from the take-off end of the conveyor 58 through the draw-ortower and thence through the outlet port 50 to the outside of the vessel 10 with the aid of therdraw-off rolls 42.

FIG. 3 illustrates an, embodiment wherein the main body portion S2 of the vessel l0 is equipped with means to effect stretching of the strand; in other words, to heat treat under tension instead of in a relaxed state as is done with the apparatus illustrated in FIG. ,2. In this case the vesselis equipped with a guide roll 62 which is positioned beneath the feed-in tower and with another guide roll 6 4 which is positioned beneath the draw-off tower. Stretching is eiiected by causing the draw-ott rolls 42 to operate at a higher peripheral speedthan that of the basket rolls 30; or, if the latter have been omitted when the heat treatment is applied to a tensioned strand, at a higher peripheral speed than that of the nip rolls 14.

A more detailed explanation will now be given of the pressure-sealing means which are located in the strandinlet and strand-outlet sections ofthe apparatus.

The prior pressure-sealing means employed in connection with conducting a strand of elongated material continuously into and out of a pressurized apparatus have not been entirely'satisfactory for one reason or another. For example,'there has been the problem of providing for the automatic adjustment of the degree of opening of the inlet port during passage ofthe strand therethrough so that knots, entanglements, etc., in the strand would pass through, atter which the diameter ofthe port would immedrately return to its original size. There has been the additional vproblem of providing sealing means which would seal theinlet and outlet ports eHectively not only when the'bundle of `iilamentary material was in the form of a round or substantially round structure but also when it was in the form of a flat band, the latter form generally being preferred because of-the greater ease in securing uniform heat treatment of the'V elongated article. Another problem has been that of obviaiting or minimizing physical damage to the strand as a result of excessive amr tions of the pressure vessel, and which has been characteristic of the prior pressure-sealing means wherein sealing was effected in one stage. These problems and difficulties are avoided by the improved pressure-sealing means of this invention.

The aforementioned pressure-sealing means are employed, itr will be understood, in apparatus for treating continuously moving strands of elongated material, more particularly a strand (e.g., a tow'or bundle) of polyacrylonitrile filamentary material, with a hot fluid medium under superatmospheric pressure in a pressure vessel having a main body portion, an inlet section at one end and an outlet section at the other end of said vessel, and also having means for introducing and conveying said elongated material into and through said inlet section, said main body pontion and said outlet section. The pressure-sealing means include pressure-buffer chambers in each of the aforementioned inlet and outlet chambers, which chambers comprise a plurality of spring-loaded gates; and fluid-supply means for supplying a uid mediumunder pressure to each of said chambers. In one embodiment of the invention thespring-loaded gates are, for example, spring-loaded eccentric aps canted in the direction of travel of the moving strands, and stops are provided to prevent over-travel of said flaps. In another embodiment of the invention the spring-loaded gates are spring-loaded slide gates which are movable in a' lateral direction and which are positioned opposite fixed gates. The loading of suchrslidegates preferably is adjustable from the exterior of the pressure vessel. In the preferred embodiment of the invention the fluid-supply means are arranged to provide a fluid medium under differing pressures to each of the pressure-buffer chambers. The pressure-buffer chamber that is closest to the main body portion of the pressure vessel is supplied with iluid medium at the highest pressure and the pressure-buffer chamber that is farthest from the main body portion on the pressure vessel is supplied with fluid medium at the lowest pressure.

1 Thus, as will be apparent from the foregoing general description and from the various figures of the accompanying drawing, the inlet and outlet sections 'of the treating vessel are divided into a plurality (two, three, four, five, six or any higher number that may be desired or required) o f pressure-buffer chambers (three are shown in the drawing) `by opening-and-shutting gates, which are movable inside and outside in the case of the inclined or canted gates or flaps; .or are slidably movable forwardly and backwardly in a direction perpendicular to the moving strand (i.e., in 'a lateral direction). The various embodiments of the pressure-sealing means are shown more-clearly in FIGS. 4, 5 and 6.

Referring particularly to FIGS. 4, 5 and 6 there is provided a casing 66 which may beconstructed of hardened stainless st eel or other material having thermal resistance, as well as resistance to chemicals and to abrasion. This casing may be in, for example, a quadrilateral tube form.

tively. The end of each arm lever is connected, respectively, through springs 92-92, 9292 and 92"-92", with each extension 94-94, 9494 and 94"-94 at the outside face of the casing 66. The doors are, thusly, so a1'- ranged as always to be closed by the restoration power of the springs whereby three pressure-butter chambers 96, 98 and 100 are formed. These chambers also may be described as being three parts or sections of a single pressure-buffer chamber.

Since it is preferable that the doors 84, 86 and 88 be inclined or canted in such a manner that they will swing in the direction of travel of the moving strand, the doors in the sealing unit 80 (FIGS. 1 and 2) of the feed-in section are canted inwardly while those in the sealing unit 82 (FIGS. 1 and 2) of the draw-olic section are canted outwardly. Suitable check bars or stops 102 advantageously are placed in the sealing units so as to restrict the inclination range of the guide plates or gates within the required limitation. In the lower part of FIG. 4 the restricted movement of the guide plates is shown by dotted lines.

In the embodiment of the invention illustrated in FIG. 6 rectangular guide plates or gates 104, 104' and 104" are fixedly attached on the inner wall of the casing 66 and perpendicular to said wall. Guide plates or gates 106, 106 and 106", which are placed directly opposite gates 104, 104' and 104, are slidably movable forwardly and backwardly by the action of the springs 108, 108' and 108, respectively. The pushing pressure of these springs is adjustable from the outside of the casing 66 by means of the rotating cap screws 110, 110 and 110". In this way there are provided movable gates directly opposite fixed gates, thus forming partitiondoors which can open or close the passageway by backward or forward movement of the gates (movable doors) 106, 106 and 106". The aforesaid partition doors are placed in parallel in three stages at adequate intervals to form three pressurebuffer chambers 118, 120 and 122.

Guide rings 124 and 126 may also be placed at the upper and lower parts of the casing to facilitatethe pas-- sage of thestrand of elongatedmaterial through the sealing unit. The surfaces of these guide rings are made smooth by well planing olf the edges where they contact the strand lest they should cause damage to the strand.

Conduits 128, 130 and 132 (FIGS. 4 and 6) provide means for introducing a pressurized medium into each of pressure-buffer chambers 96, 98 and 100 (FIG. 4) and into each of pressure-buffer chambers 118, 120 and 122 (FIG. 6), which latter is a modified form of the sealing l unit shown in FIG. 4. The pressure is so adjusted that sealing units 80 and 82 (FIGS. 1 and 2), thereby forming partition doors 84, 86 and 88. These doors can open or close the passageway by inclining motion of a pair of the guide plates 76-76, 76-76 and 76"-76. Such doors are placed in parallel in three stages at adequate intervals. The projecting parts of the rods 78-78, 78-78, and 78-78, which hold each guide plate, have arm levers 90-90, 90-90', and 90"-90" inserted therein, respecthe closer the pressure-buffer chamber is to the treating vessel 10, the higher the pressure is; and the farther the pressure-buffer chamber is from the treating vessel, the lower the pressure is. The pressure in each orf-the aforesaid pressure-buffer chambers may be induced and adjusted by any suitable means.

In the embodiments of the invention shown in FIGS. l and 2, the pressure applied to each of the pressure-buffer chambers is controlled by the pressure of varying heads of water.v Conduits 134, 136 and 138 areconnected t0 each of the water-storage tanks;140, 142 and 144, respectively, the aforesaid conduits connecting with conduits 146, 148 and 150, respectively. These latter conduits connect two of each opposite pressure-buffer chambers of the feed-in and draw-off sections of the treating vessel, so that the lower the conduit is, the greater is the head of water and, therefore, the higher the pressure. Water from a supply source (not shown) is fed into the water-storage tanks 140, 142 and 144 through the conduits 152, 154 and 156, respectively. In this Way the water level in each storage tank can be maintained at a given point and the water pressure which is thereby created is conveyed to each pressure-buffer chamber. Thus, the pressure in each buffer chamber can be adjusted and maintained where desired.

Good results are obtained by adjusting the pressure of the innermost part of the sealing unit so that itis approximately the same as that of the iiuid medium in the treating vessel, and maintaining such pressure-equilibrium conditions during operation' of the apparatus. By carrying out the pressure-buffer action stepwise through the use of a multi-stage pressure-butler chamber (or, in effect, using a ,plurality of separate pressure-buffer chambers), a satisfactorypressure seal of the vessel can be obtained while continuously passing a strand of elongated material into and out of the pressure vessel. Furthermore, damage to the strand is avoided since there is a minimum of pushing pressure or friction upon the moving strand as it passes through the movable gates or doors.

It may be also be pointed out that the upper part of y the outermost pressure-butter chamber 96 (FIG. 4) and 118 (FIG. 6) is connected to the liquid reservoir '72 and '74 (FIGS. 1 and 2), while the water flowing into the aforementioned outermost pressure-buffer chamber from the water-storage tank 140 is permitted to overflow from the said'reservoir together with the water leaking out of the Ainner pressure-butter chamber, or which leaks out of the treating vessel through the condensation of the heating medium, e.g., steam.

The discussion above is concerned particularly with the embodiments of the invention shown in FIGS. 1 and 2 and, more particularly, to the situation wherein the pressure-butter chambers are pressurized by water. However, the medium to be used :for 'the pressure-butter action advantageously is selected according to the kind and nature of the fluid medium employed for the heat-treating action in the pressure vessel 10, since such media as hot air, saturated steam, hot water, hot aqueous salt solutions of various kinds, etc., may be used for the heat-treatment depending upon such iniiuencing factors as, for example, the particular object of the heat-treatment and the kind of strand of elongated material that is to be heat-treated. In case pressurized steam is used as theheating medium, then water is suitable as the pressure-buffer medium, but saturated or Wet steam may also be used as the pressurebuffer medium.

If water, an incompressible liquid, is not existent in the pressure-buffer chambers, the multistage chambers serve as labyrinth type of apparatus to prevent leakage from the pressure vessel.

I claim:

l. A pressure-sealing device for continuously passing moving strands of elongated material therethrough between zones maintained at dierent pressures comprising:

a hollow casing having an opening at each end thereof;

a plurality of gate means subdividing said hollow casing into a plurality of chambers through which a moving strand passes in sequence in passing through said hollow casing from one end thereof to the other; and means for supplying a uid under pressure to each of `said chambers comprising means for supplying uid under a relatively higherl pressure to the chamber nearest to the zone of higher pressure and means for supplying fluid under a relatively lower pressure to the chamber nearest to the zone of lower pressure. 2. A pressure-sealing device for continuously passing moving strands of elongated material therethrough be- 8 tween zones maintained at different pressures comprising:

a hollow casing-having an inlet opening at one end thereof and an outlet opening at another end thereof, each of said openings communicating with one of said zones;

a plurality of gate means within said hollow casing subdividing said hollow casing into a plurality of chambers sequentially arranged between said inlet opening and said outlet opening; and

means for supplying iiuid to each of said chambers at a pressure intermediate the pressures adjacent to said chamber.

` 3. Apparatus as deiined in claimfZ wherein said means for supplying fluid includes:

a conduit leading to each of said chambers;

a liquid-storage tank connected to each said conduit, the

liquid-storagetank connected to the conduit leading to the chamber nearest the zone of higher pressure being at the highest elevationl and the liquid-storage tank connected to the conduit leading to the chamber nearest the zone of lower pressure being at the lowest elevation;

and means for supplying liquid to each said liquidstorage tank. Y

` 4. Apparatus as deiined inclaim 2 wherein eachof said gate means comprises a member movable between an open position and a closed position and means resiliently urging said member toward its closed position against the tendency of the moving strand to urge said member toward its open position. 5. Apparatus as dened in claim 4 wherein each of said gate means comprisesV a fixed member and a movable member slideable transversely to the direction of movement Lof said moving strand therethrough, said movable member being slidable between a closed position adjacent said iixed member and an openposition; and means for resiliently urging said movable member toward said iixed member.

' 6. Apparatus as defined in claim 4 wherein each of said gate means comprises a pair of flaps, each of said flaps being pivotably mounted near one edge thereof for movementbetween a closed position wherein the opposite edge of the ilap is adjacent the corresponding edge of its mating iiap and an open position wherein said flap is canted toward the outlet opening of saidcasing.

References Cited in the file of this patent l UNITED STATES PATENTS 

2. A PRESSURE-SEALING DEVICE FOR CONTINUOUSLY PASSING MOVING STRANDS OF ELONGATED MATERIAL THERETHROUGH BETWEEN ZONES MAINTAINED AT DIFFERENT PRESSURES COMPRISING: A HOLLOW CASING HAVING AN INLET OPENING AT ONE END THEREOF AND AN OUTLET OPENING AT ANOTHER END THEREOF, EACH OF SAID OPENINGS COMMUNICATING WITH ONE OF SAID ZONES; A PLURALITY OF GATE MEANS WITHIN SAID HOLLOW CASING SUBDIVIDING SAID HOLLOW CASING INTO A PLURALITY OF CHAMBERS SEQUENTIALLY ARRANGED BETWEEN SAID INLET OPENING AND SAID OUTLET OPENING; AND MEANS FOR SUPPLYING FLUID TO EACH OF SAID CHAMBERS AT A PRESSURE INTERMEDIATE THE PRESSURES ADJACENT TO SAID CHAMBER. 